[PR-1092][PR-1093] Optimised MCPModelClass and supports for Sdtio MCP servers

[luv-bansal]

Summary

This PR introduces a major architectural improvement to the MCPModelClass by implementing persistent session management and adding support for bridging stdio MCP servers to Python FastMCP.

Problem

The previous MCPModelClass implementation suffered from significant performance overhead:

• Created a new asyncio event loop for every request via asyncio.run()
• Opened and closed FastMCP client sessions on each request using async with self.client
• No connection reuse.
• Occasional "Session terminated" errors due to rapid session cycling

For opensourced Sdtio MCP servers, there was no built-in support in clarifai, the only way to host MCP server with Clarifai is by implementing own custom server with implementing all tools. 

Solution

1. Refactored MCPModelClass with Persistent Sessions

• Background thread with long-lived event loop: A dedicated daemon thread now owns a single asyncio event loop that runs for the entire model lifetime
• Persistent FastMCP client session: The client session is opened once during load_model() and reused for all subsequent requests
• Efficient cross-thread dispatch: Requests from the main thread are dispatched to the background loop using asyncio.run_coroutine_threadsafe()
• Proper lifecycle management: Added shutdown() method for clean resource cleanup

2. New StdioMCPModelClass for stdio MCP Servers

• Automatic tool discovery: Discovers all tools from a stdio MCP server at startup and registers them in Python FastMCP
• Single long-lived Node.js process: The stdio process (e.g., npx -y @modelcontextprotocol/server-github) starts once and stays running
• Persistent MCP session: Maintains a single ClientSession to the stdio server with double-checked locking for thread safety
• Dynamic function generation: Creates properly-typed Python functions for each stdio tool with correct signatures and annotations
• Configuration via YAML: Simple setup through config.yaml with support for environment variables and secrets

[Copilot]

Pull request overview

This PR introduces a new bridge class for integrating Node.js MCP (Model Context Protocol) servers with Python FastMCP servers within the Clarifai platform. The implementation automatically discovers and registers tools from Node.js MCP servers, making them available to MCP clients through a Python interface.

Key Changes:

• Adds NodeJSMCPModelClass that extends MCPModelClass to bridge Node.js and Python MCP servers
• Implements NodeMCPClient for communicating with Node.js MCP servers via stdio
• Provides automatic tool discovery and registration with dynamic function generation

Comments suppressed due to low confidence (2)

clarifai/runners/models/nodejs_mcp_class.py:59

• 'except' clause does nothing but pass and there is no explanatory comment.

            except Exception:

clarifai/runners/models/nodejs_mcp_class.py:63

• 'except' clause does nothing but pass and there is no explanatory comment.

            except Exception:

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 25 comments.

Comments suppressed due to low confidence (1)

clarifai/runners/models/mcp_class.py:258

• 'except' clause does nothing but pass and there is no explanatory comment.

        except Exception:

[Copilot]

@luv-bansal I've opened a new pull request, #873, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

@luv-bansal I've opened a new pull request, #874, to work on those changes. Once the pull request is ready, I'll request review from you.

[github-actions]

Package	Line Rate	Health
clarifai	45%	❌
clarifai.cli	58%	➖
clarifai.cli.templates	46%	❌
clarifai.client	67%	➖
clarifai.client.auth	67%	➖
clarifai.constants	100%	✔
clarifai.datasets	100%	✔
clarifai.datasets.export	80%	✔
clarifai.datasets.upload	75%	➖
clarifai.datasets.upload.loaders	37%	❌
clarifai.models	100%	✔
clarifai.modules	0%	❌
clarifai.rag	0%	❌
clarifai.runners	54%	➖
clarifai.runners.models	62%	➖
clarifai.runners.pipeline_steps	41%	❌
clarifai.runners.pipelines	77%	➖
clarifai.runners.utils	62%	➖
clarifai.runners.utils.data_types	72%	➖
clarifai.schema	100%	✔
clarifai.urls	60%	➖
clarifai.utils	60%	➖
clarifai.utils.evaluation	67%	➖
clarifai.workflows	95%	✔
Summary	62% (8878 / 14286)	➖

Minimum allowed line rate is 50%